The aim of this research proposal is to examine central and peripheral adaptations to the nutritional supplement creatine in older adults. Specifically, cognitive processing (e.g. memory, reaction time) and muscle function (e.g. activities of daily living (ADL), strength, power, muscle endurance, muscle contraction speed, physical activity) will be assessed in older men and women pre- and post-creatine or placebo supplementation. In the United States, approximately 750,000 older individuals will become cognitively impaired each year, and about 20% of non-institutionalized people over 70 years of age need assistance in performing at least one ADL. Levels of creatine, an amino acid derivative are reduced in the muscle, and brain of older individuals. Low muscle creatine is associated with more fatigable muscles and low brain creatine is associated with impaired memory. Following creatine supplementation, muscle and brain creatine increase, and this is associated with greater muscle mass, strength, and endurance in both young and older individuals, and improved cognitive processing, psychomotor performance, mood, balance, and cerebral oxygenation in young individuals. However, it is currently unknown if creatine supplementation can improve cognitive function (e.g. memory, reaction time), mood, or balance in older adults because research on older adults has focused on peripheral (i.e. muscular) rather than central (i.e. neurological) adaptations to creatine. Specific Aim 1: To measure cognitive processing (e.g. memory, reaction time) and mood in older participants pre- and post-creatine (0.03 g/kg body mass for 6 weeks) or placebo supplementation. Hypothesis 1: Scores on cognitive processing and mood tests will improve (e.g. improved memory, decreased reaction time) in participants ingesting creatine supplements compared to participants ingesting a placebo. Specific Aim 2: To assess performance of activities of daily living (e.g. tandem walk, chair rise time, stair climb, gate velocity) and balance in older participants pre- and post-creatine (0.03 g/kg body mass for 6 weeks) or placebo supplementation. Hypothesis 2: Performance on activities of daily living and balance tests will improve in older participants ingesting creatine supplements compared to subjects ingesting a placebo. Specific Aim 3: To measure muscular strength, power, endurance, and contraction speed in older participants pre- and post- creatine (0.03 g/kg body mass for 6 weeks) or placebo supplementation. Hypothesis 3: Muscular strength, power, endurance, and muscle contraction speed will be increased in older participants ingesting creatine supplements compared to subjects ingesting a placebo. Research Design and Methods: Men and women >65 years old will be supplemented with creatine (0.03 g/kg/d) or placebo for 6-weeks. Pre- and 6-weeks post- supplementation cognitive function (e.g. memory, reaction time, mood), muscle function (e.g. activities of daily living, strength, power, muscle endurance, muscle contraction speed, physical activity), body composition, and plasma creatine and homocysteine will be assessed. Approximately 750,000 older individuals will become cognitively impaired each year, about 20% of non-institutionalized people over 70 years of age need assistance in performing at least one activity of daily living, and more than 1/3rd of older adults fall each year, all of which reduce independence and increase the risk of premature death. The dietary supplement creatine increases muscle mass, strength, and endurance in both young and older individuals, and improves cognitive function (e.g. memory, reaction time), mood, balance, and cerebral oxygenation in young individuals. It is currently unknown if creatine supplementation can improve cognitive function, mood, or balance in older adults, but the proposed study fills this gap in the literature, and, if creatine supplementation improves cognitive function in older adults, it could have a substantial effect on the healthcare system. [unreadable] [unreadable] [unreadable]